The present invention relates generally to piston dampers, and more particularly to a magnetorheological (MR) damper.
Conventional piston dampers include MR dampers having a cylinder containing an MR fluid and having an MR piston which slideably engages the cylinder. The MR fluid passes through an orifice of the MR piston. Exposing the MR fluid in the orifice to a varying magnetic field, generated by providing a varying electric current to an electric coil of the MR piston, varies the damping effect of the MR fluid in the orifice providing variably-controlled damping of relative motion between the MR piston and the cylinder. The electric current is varied to accommodate varying operating conditions, as is known to those skilled in the art. A rod has a first end attached to the MR piston and a second end extending outside the cylinder. The cylinder and the rod are attached to separate structures to dampen relative motion of the two structures along the direction of piston travel.
A known design includes an MR piston having a magnetically energizable passageway and a magnetically non-energizable passageway, wherein the magnetically non-energizable passageway includes a check valve which is in either a valve closed position or a valve open position. The check valve blocks flow in one direction (usually when the rod moves more outward from the cylinder). The check valve allows flow in the other direction (usually when the rod moves more inward into the cylinder). This allows the MR damper to exert a different damping effect depending on the direction of rod travel.
What is needed is a magnetorheological damper having more finely-tuned damping.
In a first expression of a first embodiment of the invention, a magnetorheological damper includes a cylinder and a magnetorheological piston. The cylinder has first and second ends. The magnetorheological piston is located within, and slideably engages, the cylinder. The magnetorheological piston includes a magnetically energizable passageway and a magnetically non-energizable passageway spaced apart from the magnetically energizable passageway. The magnetorheological piston also includes a pressure and flow control valve disposed to allow pressure-dependent fluid flow in the magnetically non-energizable passageway when the piston slides towards the first end of the cylinder. In one example, the valve blocks fluid flow in the magnetically non-energizable passageway when the piston slides away from the first end of the cylinder.
In a second expression of a first embodiment of the invention, a magnetorheological damper includes a cylinder, a magnetorheological piston, and a magnetorheological fluid. The cylinder has first and second ends. The magnetorheological piston is located within, and slideably engages, the cylinder. The magnetorheological piston includes a magnetically energizable passageway and a magnetically non-energizable passageway spaced apart from the magnetically energizable passageway. The magnetorheological piston also includes a pressure and flow control valve disposed to allow pressure-dependent fluid flow in the magnetically non-energizable passageway when the piston slides towards the first end of the cylinder. A portion of the magnetorheological fluid is located in the magnetically energizable and non-energizable passageways. In one example, the valve blocks fluid flow in the magnetically non-energizable passageway when the piston slides away from the first end of the cylinder.
Several benefits and advantages are derived from the invention. The pressure and flow control valve allows pressure-dependent fluid flow in one direction meaning the valve allows for delayed valve opening until a minimum pressure is experienced, allows for full valve opening when a maximum pressure is experienced, and allows for pressure-dependent partial valve opening when a pressure between the minimum and maximum pressures is experienced. This provides for more finely-tuned damping.